Plantar fasciitis is an inflammation of the plantar fascia near the point where it attaches to the front surface of the calcaneus or heel bone. The plantar fascia becomes broader and thinner as it extends longitudinally across the bottom of the foot, eventually dividing near the heads of the metatarsal bones into five processes, one for each of the five toes. The strongest ligament in the body, the plantar fascia's purpose is to protect the softer muscles and tissues of the bottom of the foot from injury, as well as to help maintain the integrity of the foot structure itself. If the fascia becomes stretched or strained, the arch area becomes tender and swollen as well as the area about the heel bone. This inflammation is called plantar fasciitis and is typically painful from the heel throughout the arch up into the Achilles tendon. Patients suffering from this condition usually have relatively tight and inflexible heel cords, sometimes referred to as Achilles tendon tightness. When the heel cord is tight, it causes compensation in the foot with over pronation of the foot during weight bearing. The pain is consistently worse when one first arises in the morning and at the end of the day. The pain usually lurks in the heel pad and may include the arch ligament. A common tendency is to ignore the symptoms of the pain at first.
Plantar fasciitis is often caused by contracture of the Achilles tendon and the plantar fascia, which can occur at night during sleep, or during daytime inactivity. The Achilles tendon, the strongest and thickest tendon in the human body, begins at or about the middle of the posterior side of the leg extending downward towards the heel, narrowing as it progresses towards its point of insertion at the posterior surface of the os calcis. When an individual is standing, walking, running, or even sitting in a position in which the feet are in contact with the floor or other surface, both the plantar fascia and the Achilles tendon are extended to varying degrees depending of course on the nature and intensity of the activity. During sleep, an individual has a natural tendency to plantarflex the ankle joint beyond the position which is normal during walking, standing, or sitting with one's feet on the floor. Plantarflexion occurs when the bottom of the foot is extended so as to form an angle with the lower leg of greater than 90°, i.e., extend such that the forefoot moves away from the body. Dorsiflexion is the opposite motion: when the foot is moved to a position in which the bottom of the foot forms an angle with the lower leg of less than 90°, i.e., such that the top of the foot moves toward the body.
Plantar fasciitis leads to pain on weight-bearing and tenderness to deep pressure over the plantar fascia at the heel-bone junction. Additional swelling and inflammation may develop. These conditions worsen with activity. Any activity which causes the foot to spread (e.g., prolonged standing) or which causes springing of the foot (e.g., running and jumping) can aggravate the condition.
Common methods of treatment of plantar fasciitis and Achilles tendonitis include night splints and orthotic inserts. A night splint typically consists, essentially, of a strap or boot-like structure that is strapped to a patient's lower leg and a means for holding the ankle joint in dorsiflexion. In so doing, both the plantar fascia and the Achilles tendon are slightly extended and are not allowed to contract during the night. Exemplary night splints are disclosed in U.S. Pat. No. 5,399,155 (Strassburg et al.), U.S. Pat. No. 5,718,673 (Shipstead), and U.S. Pat. No. 7,753,864 (Beckwith et al.).
As the name suggests, however, night splints do not allow a sufficient range of motion, flexion, or extension to be used consistently by ambulatory users during the day. A first class of devices for ambulatory use is similar to a night splint, boot-like in appearance, and maintains the shin to foot alignment of 90 degrees or potentially wedging the toes to keep the plantar fasciitis under tension. Other devices are typically inserted between the insole of a shoe and a user's foot and utilize gel and/or foam to provide heel padding to avoid shock and distributive force, purportedly alleviating the pain associated with plantar fasciitis. Exemplary insertable devices are disclosed in U.S. Pat. No. 5,611,153 (Fisher et al.), U.S. Pat. No. 6,315,786 (Smuckler) and U.S. Publication Nos. 2004/0194348 (Campbell et al.) and 2010/0146816 (Cappaert et al.). Additional treatment devices include elastic or inelastic textile wraps with padding applied circumferentially between the forefoot and the heel. Illustrative wrap devices are disclosed in U.S. Pat. No. 5,460,601 (Shannahan) and U.S. Pat. No. 6,886,276 (Hlavac). Other devices provide particularized support to the mid-foot and arch regions, such as the devices illustrated in U.S. Pat. No. 1,538,026 (Cramer), U.S. Pat. No. 4,686,994 (Harr et al.), U.S. Pat. No. 8,162,868 (Llorens et al.), and Campbell et al.